I've written a Greasemonkey script that adds two bits of text next to the "Select: All, None, Read, Unread, Starred, Unstarred" area in Gmail. It adds Conversations and Replies to that list, so that conversations can be selected, as well as messages prefixed with Re:

The script is here and it works except that Gmail refreshes itself every so often and sometimes the links disappear.

I'm at a loss how to make the script revive and re-apply itself when this happens. How could I do this?